diff --git a/core/src/magic_string.rs b/core/src/magic_string.rs
index 325afde..d17ef54 100644
--- a/core/src/magic_string.rs
+++ b/core/src/magic_string.rs
@@ -1,6 +1,8 @@
 use std::{cell::RefCell, collections::HashMap, rc::Rc, string::ToString};
 
-use crate::utils::{normalize_index, trim};
+use crate::utils::{guess_indent, normalize_index, trim};
+
+use regex::Regex;
 
 #[cfg(feature = "node-api")]
 use napi_derive::napi;
@@ -58,6 +60,29 @@ pub struct DecodedMap {
   pub mappings: Mappings,
 }
 
+#[cfg(feature = "node-api")]
+#[derive(Debug, Clone)]
+pub struct IndentOptions {
+  pub indent_str: String,
+  pub exclude: Vec<u32>,
+}
+
+#[cfg(not(feature = "node-api"))]
+#[derive(Debug, Clone)]
+pub struct IndentOptions {
+  pub indent_str: String,
+  pub exclude: Vec<u32>,
+}
+
+impl Default for IndentOptions {
+  fn default() -> Self {
+    Self {
+      indent_str: String::from(""),
+      exclude: vec![u32::MAX, u32::MAX],
+    }
+  }
+}
+
 #[derive(Debug, Clone)]
 pub struct MagicString {
   original_str: String,
@@ -72,6 +97,8 @@ pub struct MagicString {
   last_searched_chunk: Rc<RefCell<Chunk>>,
   first_chunk: Rc<RefCell<Chunk>>,
   last_chunk: Rc<RefCell<Chunk>>,
+
+  indent_str: String,
 }
 
 impl MagicString {
@@ -104,6 +131,8 @@ impl MagicString {
       last_searched_chunk: Rc::clone(&original_chunk),
 
       original_str_locator: Locator::new(str),
+
+      indent_str: String::default(),
     }
   }
 
@@ -525,6 +554,95 @@ impl MagicString {
     Ok(self)
   }
 
+  /// ## Indent
+  /// Indents the string by the given number of spaces. Returns `self`.
+  ///
+  /// Example:
+  /// ```
+  /// use magic_string::MagicString;
+  ///
+  /// let mut s = MagicString::new("abc\ndef\nghi\njkl");
+  ///
+  /// ```
+  ///
+  pub fn indent(&mut self, option: IndentOptions) -> Result<&mut Self> {
+    let mut indent_str = option.indent_str;
+    let pattern = Regex::new(r"^\r\n")?;
+    let exclude_start = option.exclude[0];
+    let exclude_end = option.exclude[1];
+    if indent_str.len() == 0 {
+      if self.indent_str.len() == 0 {
+        self._ensure_indent_str()?;
+      }
+      indent_str = self.indent_str.clone();
+    };
+
+    let replacer = |input: &str| {
+      let mut s = input.to_string();
+      pattern.find_iter(input).for_each(|m| {
+        let start = m.start();
+        let end = m.end();
+        s.replace_range(start..end, format!("{}{}", indent_str, m.as_str()).as_str());
+      });
+      s
+    };
+    self.intro = replacer(&self.intro);
+    let mut chunk = Some(Rc::clone(&self.first_chunk));
+    let mut should_indent_next_character = true;
+    let mut char_index = 0;
+    while let Some(c) = chunk.clone() {
+      if c.borrow().is_content_edited() {
+        if !(char_index >= exclude_start && char_index <= exclude_end) {
+          let content = c.borrow().content.to_string();
+          c.borrow_mut().content = replacer(&content);
+          if content.len() != 0 {
+            should_indent_next_character = c
+              .borrow()
+              .content
+              .as_str()
+              .chars()
+              .nth(content.len() - 1)
+              .unwrap()
+              == '\n';
+          }
+        }
+      } else {
+        char_index = c.borrow().start;
+        while char_index < c.borrow().end {
+          if char_index >= exclude_start && char_index <= exclude_end {
+            char_index += 1;
+            continue;
+          }
+          let char = self
+            .original_str
+            .as_str()
+            .chars()
+            .nth(char_index as usize)
+            .unwrap();
+          if char == '\n' {
+            should_indent_next_character = true;
+          } else if char != '\r' && should_indent_next_character {
+            should_indent_next_character = false;
+            if char_index == c.borrow().start {
+              c.borrow_mut().prepend_intro(&indent_str);
+            } else {
+              self._split_at_index(char_index)?;
+              let next_chunk = c.borrow().next.clone();
+              chunk = next_chunk.clone();
+              if let Some(next_chunk) = next_chunk.clone() {
+                next_chunk.borrow_mut().prepend_intro(&indent_str);
+              }
+            }
+          }
+          char_index += 1;
+        }
+      }
+      chunk = c.borrow().next.clone();
+    }
+
+    self.outro = replacer(&self.outro);
+    Ok(self)
+  }
   /// ## Is empty
   ///
   /// Returns `true` if the resulting source is empty (disregarding white space).
@@ -685,6 +803,13 @@ impl MagicString {
 
     Ok(())
   }
+
+  pub fn _ensure_indent_str(&mut self) -> Result {
+    if self.indent_str.len() == 0 {
+      self.indent_str = guess_indent(&self.original_str)?
+    }
+    Ok(())
+  }
 }
 
 impl ToString for MagicString {
diff --git a/core/src/utils.rs b/core/src/utils.rs
index 1ecca08..4819b52 100644
--- a/core/src/utils.rs
+++ b/core/src/utils.rs
@@ -149,6 +149,8 @@ pub mod trim {
 
 use crate::{Error, MagicStringErrorType, Result};
 
+use regex::Regex;
+
 pub fn normalize_index(s: &str, index: i64) -> Result<usize> {
   let len = s.len() as i64;
 
@@ -163,3 +165,42 @@ pub fn normalize_index(s: &str, index: i64) -> Result<usize> {
 
   Ok(index as usize)
 }
+
+pub fn guess_indent(str: &str) -> Result<String> {
+  let lines: Vec<&str> = str.split('\n').collect();
+
+  let tab_pattern = Regex::new(r"^\t+")?;
+  let space_pattern = Regex::new(r"^ {2,}")?;
+
+  let spaced = lines
+    .clone()
+    .into_iter()
+    .filter(|line| space_pattern.is_match(line))
+    .collect::<Vec<&str>>();
+  let tabbed = lines
+    .clone()
+    .into_iter()
+    .filter(|line| tab_pattern.is_match(line))
+    .collect::<Vec<&str>>();
+
+  if tabbed.len() == 0 && spaced.len() == 0 || tabbed.len() > spaced.len() {
+    return Ok("\t".to_string());
+  }
+
+  let mut min: usize = 2 ^ 32;
+  for space_line in spaced {
+    let mut space_count = 0;
+    for c in space_line.chars() {
+      if c == ' ' {
+        space_count += 1;
+      } else {
+        break;
+      }
+    }
+
+    if space_count < min {
+      min = space_count
+    }
+  }
+  Ok(" ".repeat(min).to_string())
+}
diff --git a/core/tests/indent.rs b/core/tests/indent.rs
new file mode 100644
index 0000000..967d393
--- /dev/null
+++ b/core/tests/indent.rs
@@ -0,0 +1,133 @@
+#[cfg(test)]
+
+mod indent {
+  use magic_string::{IndentOptions, MagicString, OverwriteOptions, Result};
+  #[test]
+  fn should_indent_content_with_a_single_tab_character_by_default() -> Result {
+    let mut s = MagicString::new("abc\ndef\nghi\njkl");
+
+    s.indent(IndentOptions::default())?;
+    assert_eq!(s.to_string(), "\tabc\n\tdef\n\tghi\n\tjkl");
+
+    s.indent(IndentOptions::default())?;
+    assert_eq!(s.to_string(), "\t\tabc\n\t\tdef\n\t\tghi\n\t\tjkl");
+
+    Ok(())
+  }
+
+  #[test]
+  fn should_indent_content_using_existing_indentation_as_a_guide() -> Result {
+    let mut s = MagicString::new("abc\n  def\n    ghi\n  jkl");
+
+    s.indent(IndentOptions::default())?;
+    assert_eq!(s.to_string(), "  abc\n    def\n      ghi\n    jkl");
+
+    s.indent(IndentOptions::default())?;
+    assert_eq!(s.to_string(), "    abc\n      def\n        ghi\n      jkl");
+
+    Ok(())
+  }
+
+  #[test]
+  fn should_disregard_single_space_indentation_when_auto_indenting() -> Result {
+    let mut s = MagicString::new("abc\n/**\n *comment\n */");
+
+    s.indent(IndentOptions::default())?;
+
+    assert_eq!(s.to_string(), "\tabc\n\t/**\n\t *comment\n\t */");
+    Ok(())
+  }
+
+  #[test]
+  fn should_indent_content_using_the_supplied_indent_string() -> Result {
+    let mut s = MagicString::new("abc\ndef\nghi\njkl");
+    s.indent(IndentOptions {
+      indent_str: ">>".to_string(),
+      ..IndentOptions::default()
+    })?;
+    assert_eq!(s.to_string(), ">>abc\n>>def\n>>ghi\n>>jkl");
+    Ok(())
+  }
+
+  #[test]
+  fn should_prevent_excluded_characters_from_being_indented() -> Result {
+    let mut s = MagicString::new("abc\ndef\nghi\njkl");
+
+    s.indent(IndentOptions {
+      indent_str: String::from("  "),
+      exclude: vec![7, 15],
+    })?;
+    assert_eq!(s.to_string(), "  abc\n  def\nghi\njkl");
+    s.indent(IndentOptions {
+      indent_str: String::from(">>"),
+      exclude: vec![7, 15],
+    })?;
+    assert_eq!(s.to_string(), ">>  abc\n>>  def\nghi\njkl");
+    Ok(())
+  }
+
+  #[test]
+  fn should_not_add_characters_to_empty_line() -> Result {
+    let mut s = MagicString::new("\n\nabc\ndef\n\nghi\njkl");
+
+    s.indent(IndentOptions::default())?;
+    assert_eq!(s.to_string(), "\n\n\tabc\n\tdef\n\n\tghi\n\tjkl");
+
+    s.indent(IndentOptions::default())?;
+    assert_eq!(s.to_string(), "\n\n\t\tabc\n\t\tdef\n\n\t\tghi\n\t\tjkl");
+    Ok(())
+  }
+
+  #[test]
+  fn should_not_add_characters_to_empty_lines_even_on_windows() -> Result {
+    let mut s = MagicString::new("\r\n\r\nabc\r\ndef\r\n\r\nghi\r\njkl");
+
+    s.indent(IndentOptions::default())?;
+    assert_eq!(
+      s.to_string(),
+      "\r\n\r\n\tabc\r\n\tdef\r\n\r\n\tghi\r\n\tjkl"
+    );
+
+    s.indent(IndentOptions::default())?;
+    assert_eq!(
+      s.to_string(),
+      "\r\n\r\n\t\tabc\r\n\t\tdef\r\n\r\n\t\tghi\r\n\t\tjkl"
+    );
+    Ok(())
+  }
+
+  #[test]
+  fn should_indent_content_with_removals() -> Result {
+    let mut s = MagicString::new("/* remove this line */\nvar foo = 1;");
+
+    s.remove(0, 23)?;
+    s.indent(IndentOptions::default())?;
+
+    assert_eq!(s.to_string(), "\tvar foo = 1;");
+    Ok(())
+  }
+
+  #[test]
+  fn should_not_indent_patches_in_the_middle_of_a_line() -> Result {
+    let mut s = MagicString::new("class Foo extends Bar {}");
+
+    s.overwrite(18, 21, "Baz", OverwriteOptions::default())?;
+    assert_eq!(s.to_string(), "class Foo extends Baz {}");
+
+    s.indent(IndentOptions::default())?;
+    assert_eq!(s.to_string(), "\tclass Foo extends Baz {}");
+    Ok(())
+  }
+
+  #[test]
+  fn should_return_self() -> Result {
+    let mut s = MagicString::new("abcdefghijkl");
+    let result = s.indent(IndentOptions::default())?;
+
+    let result_ptr = result as *mut _;
+    let s_ptr = &s as *const _;
+
+    assert_eq!(s_ptr, result_ptr);
+    Ok(())
+  }
+}